1. Field of the Invention
The present invention relates to a musical tone generation apparatus applied to, e.g., an electronic musical instrument and, more particularly, to a musical tone generation apparatus which has hierarchical parameter memory devices for storing various parameters for characterizing musical tones to be generated, can decrease the number of rewrite times of parameters, and can rewrite parameters at high speed.
Furthermore, the present invention relates to a musical tone generation apparatus which can write data in an arbitrary channel using a random-access memory device such as a RAM regardless of a channel counter, and to a musical tone generation apparatus which uses parallel random-access memory devices to alternatively read out data from these memory devices.
2. Description of the Prior Art
In a conventional musical tone generation apparatus, various parameter values are written in a plurality of registers (parameter memory means) for storing parameters for each channel, and musical tones are generated in tone colors according to these parameters. For example, in an FM tone generator, when a musical tone is to be generated in a predetermined musical tone generation channel in a desired tone color, parameter values (e.g., tone color data) must be written in registers of the predetermined channel so as to give musical tone generation parameters such as a frequency number (F number) to a carrier operator or a modulator operator in a musical tone forming means.
In a conventional musical tone generation apparatus having the parameter memory means, a plurality of registers for storing parameters such as tone color data are prepared in one channel.
For this reason, when a tone color in one channel is to be switched, a set of parameters (tone color data) stored in the channel must be entirely rewritten. Therefore, rewrite processing exerts a heavy load on a central processing unit (CPU), and a time required for switching a tone color is undesirably prolonged.
The conventional musical tone generation apparatus employs a system for detecting a coincidence between a channel counter, and a write channel register, and generating a write signal to perform write access.
For this reason, a time corresponding to one cycle of channel counter is required at maximum for single write access of the register. For example, when the CPU successively writes parameter data in the registers, it must wait for a time corresponding to one cycle of channel counter after instruction write access of one data, and then must write the next data, thus posing a problem as to time.
The present invention has as its object to provide a musical tone generation apparatus used in, e.g., an electronic musical instrument, which apparatus can reduce a load on a CPU, and can change various parameters such as a tone color within a short period of time.
It is another object of the present invention to provide a musical-tone generation apparatus which can realize high-speed read/write access of parameters.